Ulrich Heiz - Academia.edu (original) (raw)

Papers by Ulrich Heiz

Research paper thumbnail of Same Size, Same Support, Same Spectator? Selective Acetylene Hydrogenation on supported Pd Nanoparticles

Physical chemistry chemical physics/PCCP. Physical chemistry chemical physics, 2024

Research paper thumbnail of Surface Chemistry of 1- and 3-Hexyne on Pt(111): Desorption, Decomposition, and Dehydrocyclization C

The Journal of Physical Chemistry, 2018

Research paper thumbnail of ChemInform Abstract: When Gold Is Not Noble: Nanoscale Gold Catalysts

ChemInform, Jun 10, 2010

ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Research paper thumbnail of How different are mechanisms of chemical reactions on atoms and clusters compared to their bulk analogs

Whether one can learn something about the condensed phase from clusters strongly depends on the p... more Whether one can learn something about the condensed phase from clusters strongly depends on the property under consideration. For a chem. reaction for instance subtle changes in the electronic and geometric structure when going from the atom to the bulk are detg. for the outcome of the reaction. In our exptl. studies on the chem. properties of cluster-assembled materials, metal atoms and small metal clusters are formed in the gas phase, size-selected and then deposited on thin MgO and TiO2 films grown on metal surfaces. Various chem. reactions on the obtained cluster-assembled materials are then investigated under UHV conditions by means of thermal desorption and IR spectroscopies. Oxidn. and polymn. reactions are strongly dependent on cluster size and on the cluster-support interaction, and not only the no. of product mols. per cluster is changed, but also the branching ratio of the certain reactions. In many cases the measured reactivities are different from the ones obtained for the corresponding bulk systems. In addn., first-principle calcns. are used for studying some of the chem. reactions on oxide supported metal clusters. Detailed reaction mechanisms are proposed, which describe many of the exptl. observations. Comparing the proposed reaction mechanisms with the ones for the bulk analogs can elucidate distinct differencies in the chem. behavior of clusters and condensed matter. [on SciFinder(R)]

Research paper thumbnail of Surface Chemistry of 1- and 3-Hexyne on Pt(111): Desorption, Decomposition, and Dehydrocyclization

Journal of Physical Chemistry C, Feb 19, 2018

Research paper thumbnail of Nanoassembled Model Catalysts: Changing Efficiency and Selectivity Atom-by-Atom

MRS Proceedings, 2000

Cluster-assembled materials open fascinating new routes for tuning physical and chemical properti... more Cluster-assembled materials open fascinating new routes for tuning physical and chemical properties by changing cluster size and often these materials behave completely differently than their bulk analogues. By depositing gas phase cluster cations on various surfaces, cluster model catalysts are fabricated, which exhibit remarkable catalytic activity. While inert as bulk material, gold cluster catalysts oxidize carbon monoxide with Au8 to be the smallest active size. In contrast to the high selectivity of Pd(111) surfaces for the cyclotrimerization of acetylene, small supported Pdn clusters reveal a strongly size-dependent selectivity for the polymerization of acetylene and catalyze the cyclotrimerization as well as the hydrogenation of the formed intermediate C4H4.

Research paper thumbnail of Laser Mass Spectrometry with Circularly Polarized Light: Circular Dichroism of Cold Molecules in a Supersonic Gas Beam

ChemPhysChem, Jul 8, 2014

An experiment on chiral molecules that combines circular dichroism (CD) spectroscopy, mass‐select... more An experiment on chiral molecules that combines circular dichroism (CD) spectroscopy, mass‐selective detection by laser mass spectrometry (MS), and cooling of molecules by using a supersonic beam is presented. The combination of the former two techniques (CD–laser‐MS) is a new method to investigate chiral molecules and is now used by several research groups. Cooling in a supersonic beam supplies a substantial increase in spectroscopic resolution, a feature that has not yet been used in CD spectroscopy. In the experiments reported herein, a large variation in the electronic CD of carbonyl 3‐methylcyclopentanone was observed depending on the excited vibrational modes in the n→π* transition. This finding should be of interest for the detection of chiral molecules and for the theoretical understanding of the CD of vibronic bands. It is expected that this effect will show up in other chiral carbonyls because the n→π* transition is typical for the carbonyl group.

Research paper thumbnail of 多重衝突条件下の大きなカチオン性タンタルクラスタ(Tan+,n=13~40)の酸化における二つの反応領域

Physical Chemistry Chemical Physics, 2016

Research paper thumbnail of Photochemistry of Mn2(CO)10 deposited on MgO thin films

Surface Science, Sep 1, 1998

Research paper thumbnail of Breakdown of the correlation between oxidation states and core electron binding energies at the sub-nanoscale

Research paper thumbnail of Experimental setup of a time-of-flight mass spectrometer for reaction product detection in heterogeneous catalysis

Verhandlungen der Deutschen Physikalischen Gesellschaft, 2011

Research paper thumbnail of CCDC 982397: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Research paper thumbnail of CO2-Activation by size-selected tantalum cluster cations (Ta1–16+): thermalization governing reaction selectivity

Physical Chemistry Chemical Physics, 2022

Tantalum cluster cations react with CO2 either via transfer of oxygen atoms to the clusters or th... more Tantalum cluster cations react with CO2 either via transfer of oxygen atoms to the clusters or the adsorption of an entire molecule. The released energy and vibrational heat capacities are assigned to determine the branching ratios of the pathways.

Research paper thumbnail of Enantio-enrichment of Racemic Films Using Circularly Polarized Femtosecond Pulses

Conference on Lasers and Electro-Optics, 2019

Circularly polarized laser pulses are used to desorb chiral molecules enantioselectively from an ... more Circularly polarized laser pulses are used to desorb chiral molecules enantioselectively from an achiral surface implicating the quantum mechanical nature of this process, moreover demonstrating a new method for enantio-enrichment and enantio-separation. © 2019 The Author(s)

Research paper thumbnail of 多重衝突条件下の大きなカチオン性タンタルクラスタ(Tan+,n=13~40)の酸化における二つの反応領域

Physical Chemistry Chemical Physics, 2016

Research paper thumbnail of Systematic STEM characterization of supported size-selected Pt clusters

Research paper thumbnail of Supported sub-nanometer Ta oxide clusters as model catalysts for the selective epoxidation of cyclooctene

New Journal of Chemistry, 2018

The preparation of organic ligand-free, isolated and catalytically active tantalum oxide complexe... more The preparation of organic ligand-free, isolated and catalytically active tantalum oxide complexes (Ta1) and small clusters (Tan>1) on flat silicate support was accomplished by ultra-high vacuum (UHV) techniques followed by oxidation in air.

Research paper thumbnail of Ensemble Effects in the Temperature-Dependent Photoluminescence of Silicon Nanocrystals

Chemistry - A European Journal, 2019

Research paper thumbnail of Consecutive reactions of small, free tantalum clusters with dioxygen controlled by relaxation dynamics

Physical Chemistry Chemical Physics, 2017

The reaction of small cationic tantalum clusters (Tan+, n = 4–8) with molecular oxygen is studied... more The reaction of small cationic tantalum clusters (Tan+, n = 4–8) with molecular oxygen is studied under multi-collision conditions in the gas phase, and the reaction kinetics are analyzed in order to elucidate underlying mechanisms.

Research paper thumbnail of From oxidative degradation to direct oxidation: size regimes in the consecutive reaction of cationic tantalum clusters with dioxygen

Physical Chemistry Chemical Physics, 2017

Cationic tantalum clusters (Ta9–12+) are reacted with molecular oxygen under multi-collision cond... more Cationic tantalum clusters (Ta9–12+) are reacted with molecular oxygen under multi-collision conditions in the gas phase in order to analyze the reaction kinetics.

Research paper thumbnail of Same Size, Same Support, Same Spectator? Selective Acetylene Hydrogenation on supported Pd Nanoparticles

Physical chemistry chemical physics/PCCP. Physical chemistry chemical physics, 2024

Research paper thumbnail of Surface Chemistry of 1- and 3-Hexyne on Pt(111): Desorption, Decomposition, and Dehydrocyclization C

The Journal of Physical Chemistry, 2018

Research paper thumbnail of ChemInform Abstract: When Gold Is Not Noble: Nanoscale Gold Catalysts

ChemInform, Jun 10, 2010

ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Research paper thumbnail of How different are mechanisms of chemical reactions on atoms and clusters compared to their bulk analogs

Whether one can learn something about the condensed phase from clusters strongly depends on the p... more Whether one can learn something about the condensed phase from clusters strongly depends on the property under consideration. For a chem. reaction for instance subtle changes in the electronic and geometric structure when going from the atom to the bulk are detg. for the outcome of the reaction. In our exptl. studies on the chem. properties of cluster-assembled materials, metal atoms and small metal clusters are formed in the gas phase, size-selected and then deposited on thin MgO and TiO2 films grown on metal surfaces. Various chem. reactions on the obtained cluster-assembled materials are then investigated under UHV conditions by means of thermal desorption and IR spectroscopies. Oxidn. and polymn. reactions are strongly dependent on cluster size and on the cluster-support interaction, and not only the no. of product mols. per cluster is changed, but also the branching ratio of the certain reactions. In many cases the measured reactivities are different from the ones obtained for the corresponding bulk systems. In addn., first-principle calcns. are used for studying some of the chem. reactions on oxide supported metal clusters. Detailed reaction mechanisms are proposed, which describe many of the exptl. observations. Comparing the proposed reaction mechanisms with the ones for the bulk analogs can elucidate distinct differencies in the chem. behavior of clusters and condensed matter. [on SciFinder(R)]

Research paper thumbnail of Surface Chemistry of 1- and 3-Hexyne on Pt(111): Desorption, Decomposition, and Dehydrocyclization

Journal of Physical Chemistry C, Feb 19, 2018

Research paper thumbnail of Nanoassembled Model Catalysts: Changing Efficiency and Selectivity Atom-by-Atom

MRS Proceedings, 2000

Cluster-assembled materials open fascinating new routes for tuning physical and chemical properti... more Cluster-assembled materials open fascinating new routes for tuning physical and chemical properties by changing cluster size and often these materials behave completely differently than their bulk analogues. By depositing gas phase cluster cations on various surfaces, cluster model catalysts are fabricated, which exhibit remarkable catalytic activity. While inert as bulk material, gold cluster catalysts oxidize carbon monoxide with Au8 to be the smallest active size. In contrast to the high selectivity of Pd(111) surfaces for the cyclotrimerization of acetylene, small supported Pdn clusters reveal a strongly size-dependent selectivity for the polymerization of acetylene and catalyze the cyclotrimerization as well as the hydrogenation of the formed intermediate C4H4.

Research paper thumbnail of Laser Mass Spectrometry with Circularly Polarized Light: Circular Dichroism of Cold Molecules in a Supersonic Gas Beam

ChemPhysChem, Jul 8, 2014

An experiment on chiral molecules that combines circular dichroism (CD) spectroscopy, mass‐select... more An experiment on chiral molecules that combines circular dichroism (CD) spectroscopy, mass‐selective detection by laser mass spectrometry (MS), and cooling of molecules by using a supersonic beam is presented. The combination of the former two techniques (CD–laser‐MS) is a new method to investigate chiral molecules and is now used by several research groups. Cooling in a supersonic beam supplies a substantial increase in spectroscopic resolution, a feature that has not yet been used in CD spectroscopy. In the experiments reported herein, a large variation in the electronic CD of carbonyl 3‐methylcyclopentanone was observed depending on the excited vibrational modes in the n→π* transition. This finding should be of interest for the detection of chiral molecules and for the theoretical understanding of the CD of vibronic bands. It is expected that this effect will show up in other chiral carbonyls because the n→π* transition is typical for the carbonyl group.

Research paper thumbnail of 多重衝突条件下の大きなカチオン性タンタルクラスタ(Tan+,n=13~40)の酸化における二つの反応領域

Physical Chemistry Chemical Physics, 2016

Research paper thumbnail of Photochemistry of Mn2(CO)10 deposited on MgO thin films

Surface Science, Sep 1, 1998

Research paper thumbnail of Breakdown of the correlation between oxidation states and core electron binding energies at the sub-nanoscale

Research paper thumbnail of Experimental setup of a time-of-flight mass spectrometer for reaction product detection in heterogeneous catalysis

Verhandlungen der Deutschen Physikalischen Gesellschaft, 2011

Research paper thumbnail of CCDC 982397: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Research paper thumbnail of CO2-Activation by size-selected tantalum cluster cations (Ta1–16+): thermalization governing reaction selectivity

Physical Chemistry Chemical Physics, 2022

Tantalum cluster cations react with CO2 either via transfer of oxygen atoms to the clusters or th... more Tantalum cluster cations react with CO2 either via transfer of oxygen atoms to the clusters or the adsorption of an entire molecule. The released energy and vibrational heat capacities are assigned to determine the branching ratios of the pathways.

Research paper thumbnail of Enantio-enrichment of Racemic Films Using Circularly Polarized Femtosecond Pulses

Conference on Lasers and Electro-Optics, 2019

Circularly polarized laser pulses are used to desorb chiral molecules enantioselectively from an ... more Circularly polarized laser pulses are used to desorb chiral molecules enantioselectively from an achiral surface implicating the quantum mechanical nature of this process, moreover demonstrating a new method for enantio-enrichment and enantio-separation. © 2019 The Author(s)

Research paper thumbnail of 多重衝突条件下の大きなカチオン性タンタルクラスタ(Tan+,n=13~40)の酸化における二つの反応領域

Physical Chemistry Chemical Physics, 2016

Research paper thumbnail of Systematic STEM characterization of supported size-selected Pt clusters

Research paper thumbnail of Supported sub-nanometer Ta oxide clusters as model catalysts for the selective epoxidation of cyclooctene

New Journal of Chemistry, 2018

The preparation of organic ligand-free, isolated and catalytically active tantalum oxide complexe... more The preparation of organic ligand-free, isolated and catalytically active tantalum oxide complexes (Ta1) and small clusters (Tan>1) on flat silicate support was accomplished by ultra-high vacuum (UHV) techniques followed by oxidation in air.

Research paper thumbnail of Ensemble Effects in the Temperature-Dependent Photoluminescence of Silicon Nanocrystals

Chemistry - A European Journal, 2019

Research paper thumbnail of Consecutive reactions of small, free tantalum clusters with dioxygen controlled by relaxation dynamics

Physical Chemistry Chemical Physics, 2017

The reaction of small cationic tantalum clusters (Tan+, n = 4–8) with molecular oxygen is studied... more The reaction of small cationic tantalum clusters (Tan+, n = 4–8) with molecular oxygen is studied under multi-collision conditions in the gas phase, and the reaction kinetics are analyzed in order to elucidate underlying mechanisms.

Research paper thumbnail of From oxidative degradation to direct oxidation: size regimes in the consecutive reaction of cationic tantalum clusters with dioxygen

Physical Chemistry Chemical Physics, 2017

Cationic tantalum clusters (Ta9–12+) are reacted with molecular oxygen under multi-collision cond... more Cationic tantalum clusters (Ta9–12+) are reacted with molecular oxygen under multi-collision conditions in the gas phase in order to analyze the reaction kinetics.